WoW Alliance vs. Horde
Overall, the demographic differences between Horde and Alliance characters are minimal. There are no gender differences. Male and female players are equally represented on both sides. There is a statistically significant, but substantively trivial, age difference. Players who prefer Horde characters (M = 27.5, SD = 8.0) tend to be slightly younger than players who prefer Alliance characters (M = 28.7, SD = 8.6).
Players who prefer the Horde score significantly higher on the Advancement, Competition, and Mechanics motivations than players who prefer the Alliance. In other words, players who prefer the Horde tend to be more achievement-driven, more likely to enjoy provoking and challenging each other, and more likely to be min-maxers. On the other hand, players who prefer the Alliance tend to score higher on the Role-Playing and Customization motivations than those players who prefer the Horde.
Click here for an overview of the motivations framework.